WRT to not being able to use pipenv for multiple python versions in a project - i.e. a library, it's been a couple of years since I've writing some substantial

WRT to not being able to use pipenv for multiple python versions in a project - i.e. a library, it's been a couple of years since I've writing some substantial python libraries, but do people not use tox anymore? Why can't people stick to the usual virtualenv + pip + tox routine?